The Effect of Ultrafine Red Clay Brick Pozzolan on the Microstucture of Cement Paste and its Correlation with Non-Destructive Engineering Properties

摘要

The anisotropies of Portland cement based materials are of extreme importance to determine their engineering properties. This is because interface related aspects of the cement hydration are affected by the local chemistry of the components of the matrix. The effect of such complex microstructure on the engineering parameters must be carefully examined, so that evaluation of the structure integrity can be properly made via Non Destructive Testings. The aim of this paper is to correlate the mechanical properties (destructive and non-destructive) with the microhardness of cement paste at early ages. The samples were cast using Early Strength Development Portland cement and two water to binder ratio (0.33 and 0.44 by mass). Also, two sets of cement pastes were mixed with and without a ground redbrick waste (20% by mass) pozzolan replacing cement. The test ages were 1, 3 and 7 days. The micro features of the early hydrated cement pastes were assessed by means of Scanning Electron Microscopy (Backscattered Electron Imaging Mode) and Vickers Microhardness. The data shows that the presence of the pozzolan affects the distribution of the unhydrated cement and the homogeneity of the cement matrix, yielding to different microfeatures and reflecting on the mechanical properties.